*{ box-sizing: border-box;}

.container{
    margin: 0px auto;
    width: 90%;
}

header {
    background-color:yellow;
    padding-top: 2em;
    text-align: center;
    height: 200px;
}

main{
    display: flex;
    flex-wrap: wrap;
}

.red{
    width: 100%;
    height: 200px;
    background-color: red;
}

.blue{
    width: 100%;
    height: 200px;
    background-color:blue;
}

.pink{
    width: 100%;
    height: 200px;
    background-color: rgb(128, 0, 96);
}

.green{
    width: 100%;
    height: 200px;
    background-color: green;
}

@media screen and (min-width: 576px){
    main{
        display: flex;
        flex-wrap: wrap;
    }
    .red, .blue, .pink{
        width: 50%;
    }
    .green{
        width: 50%;
    }
}

@media screen and (min-width: 993px){
    main{
        display: flex;
        flex-wrap: wrap;
    }
    .red, .blue, .pink{
        width: 25%;
    }
    .green{
        width: 25%;
    }
}
@media screen and (orientation:landscape){
    header{
        background-color: rgb(150, 76, 211);
        color: rgb(228, 245, 228);
    }
}